Usage:
Schwitzer and AiResearch Turbochargers
- SUPPLEMENT: 04/06/77
ENGINE NEWS, MARCH 15, 1977, PAGE 2.
In the article "Changes To Retainer Nut Torque And Assembly Procedures For Turbocharger Compressor Wheels" change the first paragraph about the "Reference Article:" to read: "Reference Article: "New Retaining Nuts For Turbocharger Compressor Wheel", Engine News, December 8, 1976".
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Reference: "New Retaining Nuts For Turbocharger Compressor Wheel", Engine News, December 8, 1976.
Schwitzer Turbochargers
The reference article tells about the use of a new retainer nut for the compressor wheel on Schwitzer turbochargers, and gives torque values for the nuts on most models. The new nut is larger across the hex so it has more contact surface, and is machined with improved precision for maximum contact with the compressor wheel. With this improved design, the self-locking type nut and the washer are not needed. During turbocharger reconditioning, it is best to use the new nut in place of the former nut and washer. The new nut has a copper color for identification.
A complete list of torque values is shown in the chart for easy reference. These torque values can be used for the compressor wheel nut on all earlier turbochargers of the models shown. The torque shown for some models is now the same as it was before a former recommendation was made to increase the torque. The torque recommendation is changed back to the lower value because the higher torque caused damage to some compressor wheels where larger amounts of metal had been removed for wheel balance. For some other models, a common torque is now used in place of the former different torque recommendations. See the chart for torque values, and the topic "Disassembly and Assembly".
AiResearch Turbochargers
A change has been made to the design of the shaft in models T12, TV61, TW61, T18, TV81 and TW81 turbochargers. The new design permits the compressor wheel to be assembled on the shaft at room temperature, so it is not necessary to heat the wheel for installation. During assembly, either of two methods can be used to check a unit for this later design shaft:
1. Fit the compressor wheel on the shaft by hand, then measure the length of shaft threads that extend beyond the wheel. If there is .25 in. (6.4 mm) or more of threads extended, the wheel can be installed at room temperature.
2. Assemble the correct thrust collar and seal carrier spacer on the shaft, then fit the compressor wheel on the shaft by hand and measure the distance between the wheel and seal carrier spacer. This can be done before the shaft is installed in the center housing. If the measured distance is .31 in. (7.9 mm) or less, the wheel can be installed at room temperature.
To install the compressor wheel at room temperature on a later shaft, assemble the wheel on the shaft as far as it will go, then install the retainer nut and tighten to the "initial (first) torque" shown in the chart. Remove the nut, put a small amount of oil on the threads and nut seat face, then install the nut again. Tighten the nut to the "final (last) torque" plus the "added turn" shown in the chart. Also, see the topic "Disassembly and Assembly".
When the compressor wheel will not slide easily on the shaft to the dimension given in one of the above procedures, it must be heated for installation. Heat the wheel to 350 ± 25°F (177 ± 14°C) for not more than ten minutes, then install it on the shaft and tighten the retainer nut to the "initial (first) torque" shown in the chart while the wheel is hot. After the wheel is cool (at a temperature less than 150°F-66°C), remove the nut, put a small amount of oil on the threads and nut seat face, then install the nut again. Tighten the nut to the "final (last) torque" plus the "added turn" shown in the chart. Also, see the topic "Disassembly and Assembly".
For model TO4 turbochargers, the compressor wheel is a free fit on the shaft and it is not necessary to heat the wheel or tighten the nut to an "initial (first) torque". Assemble the compressor wheel on the shaft, put a small amount of oil on the threads and nut seat face, then install the retainer nut. Tighten the nut to the "final (last) torque" plus the "added turn" shown in the chart. Also, see the topic "Disassembly and Assembly".
Disassembly And Assembly (All Turbochargers)
Use caution at all times to prevent bend stresses on the shaft, damage to the bore in the compressor wheel, or any other damage to components during turbocharger disassembly and assembly. Generally (except on AiResearch model TO 4 turbochargers), force must be used to remove the compressor wheel from the shaft, and any damage to the shaft or wheel can cause failure of the rebuilt turbocharger. When a press is used to push the shaft out of the wheel, release the pressure at short intervals to permit tool alignment, release any side forces, and prevent contact between the press tool and the bore in the compressor wheel.
During assembly of the compressor wheel and retainer nut on the shaft, be very careful to prevent bend stresses on the shaft. The recommendation is to use a universal joint between the torque wrench and the socket, and hold the wrench with both hands. The universal joint makes it easier to turn the nut without the application of side force on the shaft.
